Spectral imaging using illumination of preselected spectral content

Abstract

A device and method for spectral imaging of an object. A plurality of sets of narrow-band light sources such as LEDs are provided. Each set emits illumination radiation in a different narrow spectral band. Each set is activated sequentially to illuminate the object. Light reflected from the object or transmitted by the object is focused on a detector array to image the object. Narrower illumination bands are provided by dispersing the emitted light using a dispersive optical element such as a diffraction grating. Alternatively; selected sets or subsets are activated simultaneously with duty cycles that emulate a preselected spectral distribution. For imaging ocular fundus tissue, the illumination light is shaped into an annular beam by an appropriately shaped waveguide.

What is claimed is: 
     
       1. A device for spectral imaging of an object, comprising: (a) a plurality of sets of light sources for producing light in a like plurality of separate spectral bands, each of said sets including at least one of said light sources for emitting light in said spectral band of said each set;   (b) an illumination mechanism for directing at least a portion of said emitted light at the object, thereby illuminating the object, the object producing radiated light in response to said illumination, said illumination mechanism being operative to direct said emitted light from all of said sets at a common line, said illumination mechanism including a waveguide having a linear input end coincident with said common line, said waveguide including a plurality of optical fibers; and   (c) an imaging mechanism for detecting said radiated light and transforming said radiated light into at least one image of the object.   
     
     
       2. The device of claim 1, wherein said light sources include LEDs. 
     
     
       3. The device of claim 1, wherein said illumination mechanism includes a diffraction grating. 
     
     
       4. The device of claim 3, wherein said diffraction grating is operative to select a subband of at least one of said spectral bands for said illumination of the object. 
     
     
       5. The device of claim 1, wherein said illumination mechanism is operative to direct an annular beam of said at least portion of said emitted light at the object. 
     
     
       6. The device of claim 5, wherein said illumination mechanism includes a waveguide having an annular output end for forming said annular beam. 
     
     
       7. The device of claim 6, wherein said waveguide includes a plurality of optical fibers, each of said optical fibers having an output end, said output ends being disposed along a circle to form said annular output end of said waveguide. 
     
     
       8. The device of claim 1, wherein said imaging mechanism includes an array of detectors. 
     
     
       9. The method of claim 8, wherein said array is two-dimensional. 
     
     
       10. The device of claim 1, incorporated in a medical imaging apparatus. 
     
     
       11. The device of claim 10, wherein said medical imaging apparatus is a fundus camera. 
     
     
       12. The device of claim 10, wherein said medical imaging apparatus is an endoscope. 
     
     
       13. The device of claim 1, wherein each of said sets includes at least two of said light sources. 
     
     
       14. The device of claim 1, wherein each said at least one image is two-dimensional. 
     
     
       15. A method of imaging an object, comprising the steps of: (a) producing illumination light in a plurality of spectral bands, using, for each of said spectral bands, at least one light source specific to said each spectral band;   (b) illuminating the object with at least a portion of said illumination light, the object producing radiated light in response to said illumination light; and   (c) detecting said radiated light so as to produce at least one image of the object; wherein the object is illuminated successively in accordance with a plurality of preselected spectral distributions, the object being illuminated simultaneously with said illumination light of said spectral bands in accordance with each said preselected spectral distribution, said successive illuminating of the object in accordance with said plurality of preselected spectral distributions being effected at least twice.     
     
     
       16. The method of claim 15, wherein each of said at least one light source includes an LED. 
     
     
       17. The method of claim 15, wherein the object is illuminated sequentially with said illumination light of each of said spectral bands. 
     
     
       18. The method of claim 17, wherein said detecting of said radiated light is coordinated with said sequential illumination to produce, for each said spectral band, a corresponding said at least one image of the object. 
     
     
       19. The method of claim 15, wherein said spectral distribution is preselected by steps including decorrelation of a plurality of reflectivity spectra. 
     
     
       20. The method of claim 15, wherein said illuminating of the object is effected by steps including: (i) forming an annular beam of said illumination light, and   (ii) directing said annular beam at the object.   
     
     
       21. The method of claim 20, wherein said forming of said annular beam is effected by steps including: (A) providing a waveguide including an input end and an annular output end, and   (B) introducing said illumination light to said input end of said waveguide, said illumination light then emerging from said output end of said waveguide as said annular beam.   
     
     
       22. The method of claim 15, wherein said producing of said illumination light is effected by operating said at least one light source of said each spectral band according to a duty cycle that results in said illuminating of the object being effected with a preselected spectral distribution. 
     
     
       23. The method of claim 22, wherein said spectral distribution includes a plurality of said spectral bands. 
     
     
       24. The method of claim 15, wherein said producing of said illumination light is effected by providing said at least one light source of said each spectral band with an electrical current level that results in said illuminating of the object being effected with a preselected spectral distribution. 
     
     
       25. The method of claim 24, wherein said spectral distribution includes a plurality of said spectral bands. 
     
     
       26. The method of claim 15, wherein said illumination is produced using at least two said light sources specific to each said spectral band. 
     
     
       27. The method of claim 15 wherein each said at least one image is two-dimensional. 
     
     
       28. The method of claim 15, wherein said spectral distribution includes a plurality of said spectral bands. 
     
     
       29. A method of imaging eye tissue of an eye including a pupil, comprising the steps of: (a) producing illumination light in a plurality of spectral bands, using, for each of said spectral bands, at least one light source specific to said each spectral band;   (b) forming an annular beam of said illumination light;   (c) directing said annular beam at the eye tissue via the pupil to illuminate the eye tissue sequentially with said illumination light of each of said spectral bands;   (d) collecting light reflected from the eye tissue via the pupil; and   (e) detecting said reflected light so as to produce at least one image of the eye tissue, said detecting of said reflected light being coordinated with said sequential illumination to produce, for each said spectral band, a corresponding said at least one image of the eye tissue.   
     
     
       30. The method of claim 29, wherein each of said at least one light source includes an LED. 
     
     
       31. The method of claim 29, wherein the eye tissue is illuminated simultaneously with said illumination light of said spectral bands in accordance with a preselected spectral distribution. 
     
     
       32. The method of claim 31, wherein the eye tissue is illuminated successively in accordance with a plurality of said preselected spectral distributions. 
     
     
       33. The method of claim 32, wherein said successive illuminating of the eye tissue in accordance with said plurality of said preselected spectral distributions is effected at least twice. 
     
     
       34. The method of claim 31, wherein said spectral distribution is preselected by steps including decorrelation of a plurality of reflectivity spectra. 
     
     
       35. The method of claim 31, wherein said spectral distribution includes a plurality of said spectral bands. 
     
     
       36. The method of claim 29, wherein said forming of said annular beam is effected by steps including: (i) providing a waveguide including an input end and an annular output end, and   (ii) introducing said illumination light to said input end of said waveguide, said illumination light then emerging from said output end of said waveguide as said annular beam.   
     
     
       37. The method of claim 29, wherein said producing of said illumination light is effected by operating said at least one light source of said each spectral band according to a duty cycle that results in said illuminating of the object being effected with a preselected spectral distribution. 
     
     
       38. The method of claim 37, wherein said spectral distribution includes a plurality of said spectral bands. 
     
     
       39. The method of claim 29, wherein said producing of said illumination light is effected by providing said at least one light source of said each spectral band with an electrical current level that results in said illuminating of the object being effected with a preselected spectral distribution. 
     
     
       40. The method of claim 39, wherein said spectral distribution includes a plurality of said spectral bands. 
     
     
       41. The method of claim 29, wherein said illumination is produced using at least two said light sources specific to each said spectral band. 
     
     
       42. The method of claim 29, wherein each said at least one image is two-dimensional. 
     
     
       43. A method of imaging an object having at least one of a plurality of features, each of the features having a certain reflectivity spectrum, comprising the steps of: (a) producing illumination light in a plurality of spectral distributions, each said spectral distribution being in accordance with at least one of the reflectivity spectra;   (b) illuminating the object with said illumination light successively at each of said plurality of spectral distributions, the object producing radiated light in response to said illumination; said successive illuminating of the object at each said spectral distribution being effected at least twice, and   (c) detecting said radiated light so as to produce at least one image of the object.   
     
     
       44. The method of claim 43, wherein said producing of said illumination light is effected using a plurality of sets of at least one light source, said at least one light source of each said set all emitting in a common spectral band, each said set emitting in a different spectral band. 
     
     
       45. The method of claim 44, wherein each said set includes at least two said light sources. 
     
     
       46. The method of claim 43, wherein each of said at least one source includes an LED. 
     
     
       47. The method of claim 43, wherein said spectral distribution is obtained by steps including decorrelation of said reflectivity spectra. 
     
     
       48. The method of claim 43, wherein said spectral distribution includes a plurality of spectral bands. 
     
     
       49. The method of claim 43, wherein each said at least one image is two-dimensional. 
     
     
       50. An improved fundus camera of the type in which an annular beam of light is directed at eye tissue and light reflected from the eye tissue travels axially through the annular beam, the improvement comprising a waveguide having an annular output end wherefrom the annular beam of light emerges, said waveguide including a plurality of optical fibers. 
     
     
       51. The fundus camera of claim 50, wherein said waveguide has a linear input end. 
     
     
       52. The fundus camera of claim 50, wherein said waveguide includes an aperture wherethrough the reflected light travels. 
     
     
       53. The fundus camera of claim 50, wherein each of said optical fibers has an output end, said output ends being arranged along a circumference of a circle to produce the annular beam of light. 
     
     
       54. A method of imaging an object having a plurality of features, each feature having a reflectivity spectrum from among a larger plurality of reflectivity spectra, comprising the steps of: (a) producing illumination light at each of a plurality of spectral distributions, each of said spectral distributions being in accordance with at least one of said larger plurality of reflectivity spectra, said plurality of spectral distributions being obtained by steps including decorrelation of said larger plurality of reflectivity spectra;   (b) successively illuminating the object with said illumination light at each of said plurality of spectral distributions, the object producing radiated light in response to said illumination; and   (c) detecting said radiated light so as to produce at least one image of the object.   
     
     
       55. The method of claim 54, wherein said successive illuminating of the object at said each spectral distribution is effected at least twice. 
     
     
       56. The method of claim 54, wherein each said at least one image is two-dimensional. 
     
     
       57. The method of claim 54, wherein each said spectral distribution includes a plurality of spectral bands. 
     
     
       58. A device for spectral imaging of an object, comprising: (a) a plurality of sets of light sources for producing light in a like plurality of separate spectral bands, each of said sets including at least one of said light sources for emitting light in said spectral band of said each set;   (b) an illumination mechanism for directing an annular beam of at least a portion of said emitted light at the object, thereby illuminating the object, said illumination mechanism including a waveguide that includes a plurality of optical fibers, each of said optical fibers having an output end, said output ends of said optical fibers being disposed along a circle to form an annular output end of said waveguide for forming said annular beam, the object producing radiated light in response to said illumination; and   (c) an imaging mechanism for detecting said radiated light and transforming said radiated light into at least one image of the object.   
     
     
       59. A device for spectral imaging of an object, comprising: (a) a plurality of sets of light sources for producing light in a like plurality of separate spectral bands, each of said sets including at least one of said light sources for emitting light in said spectral band of said each set;   (b) an illumination mechanism for directing at least a portion of said emitted light at the object, thereby illuminating the object, the object producing radiated light in response to said illumination; and   (c) an imaging mechanism for detecting said radiated light and transforming said radiated light into at least one image of the object; wherein the device is incorporated in a fundus camera.     
     
     
       60. A device for spectral imaging of an object, comprising: (a) a plurality of sets of light sources for producing light in a like plurality of separate spectral bands, each of said sets including at least one of said light sources for emitting light in said spectral band of said each set;   (b) an illumination mechanism for directing at least a portion of said emitted light at the object, thereby illuminating the object, the object producing radiated light in response to said illumination; and   (c) an imaging mechanism for detecting said radiated light and transforming said radiated light into at least one image of the object; wherein the device is incorporated in an endoscope.     
     
     
       61. A method of imaging an object, comprising the steps of: (a) producing illumination light in a plurality of spectral bands, using, for each of said spectral bands, at least one light source specific to said each spectral band;   (b) illuminating the object with at least a portion of said illumination light, the object producing radiated light in response to said illumination light; and   (c) detecting said radiated light so as to produce at least one image of the object; wherein the object is illuminated simultaneously with said illumination light of said spectral bands in accordance with a spectral distribution that is preselected by steps including decorrelation of a plurality of reflectivity spectra.     
     
     
       62. A method of imaging eye tissue of an eye including a pupil, comprising the steps of: (a) producing illumination light in a plurality of spectral bands, using, for each of said spectral bands, at least one light source specific to said each spectral band;   (b) forming an annular beam of said illumination light;   (c) directing said annular beam at the eye tissue via the pupil to illuminate the eye tissue;   (d) collecting light reflected from the eye tissue via the pupil; and   (e) detecting said reflected light so as to produce at least one image of the eye tissue; wherein the eye tissue is illuminated successively in accordance with a plurality of preselected spectral distributions, the eye tissue being illuminated simultaneously with said illumination light of said spectral bands in accordance with each said preselected spectral distribution, said successive illuminating of the object in accordance with said plurality of preselected spectral distributions being effected at least twice.     
     
     
       63. A method of imaging eye tissue of an eye including a pupil, comprising the steps of: (a) producing illumination light in a plurality of spectral bands, using, for each of said spectral bands, at least one light source specific to said each spectral band;   (b) forming an annular beam of said illumination light;   (c) directing said annular beam at the eye tissue via the pupil to illuminate the eye tissue;   (d) collecting light reflected from the eye tissue via the pupil; and   (e) detecting said reflected light so as to produce at least one image of the eye tissue; wherein the eye tissue is illuminated simultaneously with said illumination light of said spectral bands in accordance with a spectral distribution that is preselected by steps including decorrelation of a plurality of reflectivity spectra.     
     
     
       64. A method of imaging an object having at least one of a plurality of features, each of the features having a certain reflectivity spectrum, comprising the steps of: (a) producing illumination light having a spectral distribution in accordance with at least one of the reflectivity spectra, said spectral distribution being obtained by steps including decorrelation of said at least one reflectivity spectrum;   (b) illuminating the object with said illumination light, the object producing radiated light in response to said illumination; and   (c) detecting said radiated light so as to produce at least one image of the object.   
     
     
       65. A method of imaging an object having a plurality of features, each feature having a reflectivity spectrum from among a larger plurality of reflectivity spectra, comprising the steps of: (a) producing illumination light at each of a plurality of spectral distributions, each of said spectral distributions being in accordance with at least one of said larger plurality of reflectivity spectra;   (b) successively illuminating the object with said illumination light at each of said plurality of spectral distributions, the object producing radiated light in response to said illumination, said successive illuminating of the object at each said spectral distribution being effected at least twice; and   (c) detecting said radiated light so as to produce at least one image of the object.